Human Contributions to Environmental Change

By Ian James

Human impacts on the environment cannot be understood simply under the guises of climate change, pollution, land degradation or changes to global biogeochemical cycles. Whilst these problems are often treated as independent from one another, what we know about systems within the atmosphere and ecosphere suggests that issues of climate and environmental change are inseparable and that they often positively feed back into one another (Meadows, 2008). Increased emissions accelerate environmental degradation, and increased environmental degradation accelerates atmospheric change.

In order to understand how and why we need to change, we should look at the extent to which humans are responsible for global environmental and atmospheric changes. A common talking point from those looking to downplay the severity of human impact on both the atmosphere and ecosphere is to point to the fact that both the climate and the environment have always been changing. This is why the scientific community differentiates between anthropogenic forcings (e.g. emissions from transportation) and natural forcings (e.g. changes in the radiative output of the sun) of temperature (UCSUSA, 2017). It is easy to point to changes that have occurred as the result of human activity and mistake them for natural variance due to the removed degrees of culpability provided by complex interactive systems. However, there is an important difference between variability and unprecedented change.

A helpful place to look to dispel current climate change myths is to compare the extent and speed of change across former geological epochs with that of our current epoch – the Anthropocene. The term Anthropocene refers to the effect of humans on the planet since 1610 that has been severe enough to propel us into a new geological category (Lewis & Maslin, 2015). Certainly there have been periods in Earth’s history with equivalent atmospheric CO2 concentrations to today – four of history’s previous five mass extinction events are attributable to climate change, but the speed of the Anthropocene extinction far outdoes anything within the realms of natural variability (Battarbee, 2008).

Across the history of species there has been a background rate of extinction. This refers to the amount of species, on average, that go extinct in any given year. It is estimated that due to the effects of anthropogenic environmental change, the current extinction rate is 1000-10,000 higher than it was prior to the Anthropocene (Vos, Joppa, Gittleman, Stephens, & Pimm, 2015; Lamkin & Miller, 2016). Species loss destabilises ecosystems and decreases the availability of ecosystem services for humanity, prompting further destruction in response to dwindling resource flows (Cardinale & al, 2012).

We know that humanity is responsible for the vast majority of greenhouse gas emissions because emissions can be measured. The pre-industrial baseline for CO2 concentrations in the atmosphere is 280ppm, the current level is over 400ppm, a change of 120ppm since the industrial revolution and the highest concentration level for at least 750,000 years (Battarbee, 2008). Changes in the relative abundance of different carbon isotopes in the atmosphere show that the vast majority of carbon increase is a result of fossil fuel combustion (UCSUSA, 2017). Overall, roughly two-thirds of the negative effects resulting from atmospheric and oceanic warming can be reliably attributed to human activity (Hansen & Stone, 2016). The primary drivers of increased emissions are transportation, electricity, industry, land use change and agriculture.

Whilst the interconnectivity of the issues of climate change and ecological crisis may seem to place us in a hopeless situation, it is also important to note that what presently forms a potential runaway scenario of self-reinforcing processes can also be viewed as an opportunity to create a virtuous spiral in which every stone will kill at least two birds.

Bibliography

Battarbee, R. W. (2008). Holocene Climate Variability and Global Warming. In R. W. Battarbee, & H. A. Binney, Natural climate variability and global warming a Holocene perspective (pp. 1-7). Malden MA: Blackwell.

Cardinale, B. J., & al, e. (2012). Biodiversity loss and its impact on humanity. Nature Vol. 486 No. 7401 , 59-67.

Hansen, G., & Stone, D. (2016). Assessing the observed impact of anthropogenic climate change. Nature Climate Change 6, 532-537.

Lamkin, M., & Miller, A. I. (2016). On the Challenge of Comparing Contemporary and Deep-Time Biological-Extinction Rates. Bioscience 66(9), 785-789.

Lewis, S. L., & Maslin, M. A. (2015). Defining the Anthropocene. Nature Vol. 519 Issue. 7542, 171-180.

Meadows, D. H. (2008). Thinking in Systems: A Primer. White River Junction: Chelsea Green Publishing.

UCSUSA. (2017). How Do We Know that Humans Are the Major Cause of Global Warming? Cambridge MA: Union of Concerned Scientists.

Vos, J. M., Joppa, L. N., Gittleman, J. L., Stephens, P. R., & Pimm, S. L. (2015). Estimating the normal background rate of species extinction. Conservation Biology 29(2), 452-462.